Seam reducing



c. K. M cDoNALD Nov. 28, 1939.

5 EM REDUC ING FiledDec. 2, 193'? Patented Nov. 28, 1939 UNITED STATESSEAM REDUCING Glifiord K. MacDonald, Brockton, Mass, assign-" or toUnited Shoe Machinery Corporation, Borough of Flemington, N. J., a.corporation of New Jersey Application December 2, 1937, Serial No.177,768'

10 Claims.

This invention relates to reducing the seams of articles of leather andthe like and is herein illustratively described as applied to thereduction of the back seams of shoes.

One very common method of forming a seam in articles of leather orleather-like material is by placing the pieces face to face andstitching through the two layers closely adjacent to the edges thereof.Commonly, the sewing machine is equipped with a trimming knife whichremoves part of the surplus material and leaves projecting margins ofuniform and equal width when the two pieces have been joined. Such seamsare found in many articles, such as handbags, luggage, harnesses andthelike, and are almost uni-.

- cause of the fibrous appearance of the edge of the leather or othersimilar material and the fact that there is often a gradation of colorfrom one face of a piece of leather through to the other face. Asapplied to shoes, the projecting mar gins of the seam are inside theshoe and it is desirable to make themas low as possible without eitherdistorting the seam or pressing it so hard that the stitches smile i.e-., are visible on the outside of the shoe. Obviously, too, thestrength of the seam must not be diminished by anytreatment which isimparted to it.

It is therefore an object of the invention to produce an improved seamhaving a good appearance when it is an exposed seam and lying as fiat aspossible and to do this Without reducing the strength of the'seam. Stillanother object of the invention is to provide an improved method ofreducing seams by means of which the desired results may be securedexpeditiously and with a minimum of skill. To these ends, I havediscovered that a seam of thedesired characteristics may be obtained bythe application to the edgeof the seam of heat to a degree sufficient tosear and char the leather.. Under this application of heat, lasting onlya short time,ithe leathenwill become slightlyplastic and may, bytheapplication of pressure, be molded to spread and flatten the seam.The seam willat the sametime become shrunken and compacted so that thesurface of the treated edges is substantially bone hard. This results inproducing a finished. appearance on the edges'of the seam and a surfacewhich is not easily marred since it is hard enough so that when testedwith the edge of the fingernail of an observer, only a slight mark willbe made on the surface and no substantial crease will result.

It is another object of the invention to provide a machine by means ofwhich the above-described process may be carried out. Such a machine asherein illustrated comprises a work feeding mechanism designed tosupport the work and carry it along in the desired direction. Adjacentto the feeding mechanism is a searing tool arranged to bepressed firmlyagainst the edges of the upstanding margins of the seam, there beingprovision for heating this tool by the application to the upper surfacethereof of an oxyacetylene flame so that it becomes at least red hot.Preferably the work-engaging surface of the searing tool is grooved atits receiving end to guide into position the upstanding margin of theseam, and the operative face of the tool is corrugated to assist inremoving charred portions of the leather which are produced by theapplication of a considerable heat.

A machine by means of which the method may readily be practiced will nowbe described in the following specification, taken in connection withthe accompanying drawing, inwhich Fig. 1 is an end View of the operativeportion of such a machine; 1

Fig. 2 is a view of the portion shown in Fig. 1 viewed from the rightand looking in the direction inwhich the work moves Fig. Sis afragmentary view of the operating tools, showing a piece of work beingtreated;

Fig. 4 is an angular View on a much enlarged scale of the'searing tool,showing particularly'the under face thereof; y

Fig. 5 shows a fragment of anuntreated seam,

and

Fig. 6.illustrates approximately the condition 1 of the seam aftertreatment, it being understood that the exact shape depends on a numberof factors and, hence, is subject to variation.

When pieces of work A and B, having finished surfaces If] and I2 placedface to face, are joined together by meansof a row of stitches S, there-- sulting seam includes upstanding margins it having exposed edgesl6" of substantially the thickness of the pieces of material. Theseedges, produced usually by a trimming knife on the sewing machine, arebrought asclose to the stitches S. as is considered safe, having regardto thedanger of damage to the seam itself and the resulting strength.Obviously, the exposed edges U5 are fibrous and do not present afinished appearance since there may be a gradation of color from thesurfaces l0 and I2, which are often the grain surfaces, to theunfinished or flesh surfaces l8. In previously employed methods oftreatment, these margins have been compacted by means of pressure andheat, the pressure being applied both laterally and heightwise andtending to shrink the leather of the upstanding margins l4 slightly.Such heat as has been employed, however, has not beenof a destructivetemperature. Furthermore, it has been diffioult, having in mindparticularly the back seams of shoes, to compress the seam heightwisewithout, at the same time, applying such pressure to the outer surfaceof the shoe that the two pieces of leather are pushed away from oneanother with the danger of leaving an unsightly seam in which thestitches smile.

I have discovered, however, that it is possible to apply a destructivetemperature momentarily to the seam, said temperature being of the orderof from l200 to 1500 F., and thereby to shrink, sear and char the seamwithout in any way a1- fecting its strength.

As one suitable way of applying heat to the seam, I have utilized amodified machine of the type of that shown in Letters Patent of theUnited States No. 2,017,055, granted October 15, 1935, on theapplication of Doulette and Hooper and reference may be had to thatpatent for a description of such parts of the machine as are not hereinfully shown or described. The patented machine is designed for thetreatinment of leather edges, heat being applied to the flesh orunfinished surface of the leath along a line slightly spaced from theedge, thereby causing the edge to shrink and the grain or finishedsurface to bend over to meet the level of the unfinished surface. Inthis machine, the work is supported on a substantially cylindrical feedroll 20 driven in the direction of the arrow shown in Fig. 1, and thework is held on this supporting feed roll by means of a thin tootheddisk 22 which engages the flesh surface of the leather and is in turndriven through gears 24 and 26 by power suppliedthrough a shaft 28. Thefeed wheel 22, and the v driving mechanism therefor, are mounted in ahead 30 which is capable of being raised and lowered for convenience inthe insertion of the work and which is urged down resiliently to holdthe feed wheel against the work.

Adjacent to the narrow feed wheel 22, there is. as in the patentedmachine, a searing tool 32, the form of which has, however, beenradically changed. The searing tool has upstanding legs 34 enabling itto be clamped in a holder 36, which, by reason of .a constructioninvolving sliding joints and screws 38 and 40, may be adjusted fromfront to back and from side to side as in the patented machine. Thisholder is urged downwardly to press the searing tool 32 against the workby means of a spring (not shown) which imparts a pressure of from twentyto thirty pounds. It will be noted that the tool at its receiving orrear end, considered with respect to the direction of movement of thework, has a tapered entrance groove 42 facilitating the introduction ofthe upstanding margin l4 of the seamforwardly along the desired path.Inasmuch as the tool is heated to a red or cherry heat by an arrangementto be described, it has been found desirable to provide the surface ofthe tool beyond the entrance groove 42 with cor-' rugations or grooves44 extending transversely and grooves 45 extending lengthwise of thetool thereby assisting in the removal of charred material and enablingthe tool to trim the work or reduce the seam under the destructiveaction of heat. Because substantial pressure is being applied to theseam through this tool, there will be a molding action on the leather ata time when it is in a momentarily plastic condition which will tend tospread the seam laterally, leaving overhanging lips 46 which apparentlytend to protect the stitches S from the applied heat. At any rate, ithas been found that the seam ridge may be reduced to a point where itssurface is spaced only six to eight thousandths of an inch from thestitches S without any damage to the thread or any weakening of itsholding power. The surface 48 of the reduced seam is seared and charredso that it is substantially bone hard, as has been heretofore broughtout. At the same time, due to the action of the corrugations 44 inremoving or trimming off the charred material, this surface 48 is onlyslightly discolored and its appearance is radically improved because ofthe shrinking and compacting action of the heat on the fibers of theleather. This shrinking action affects .the leather to a substantialdistance below the surface 48 and the strength of the seam is improvedrather than lessened as it has been found that when test pieces arepulled in a direction transversely of the seam until a failure takesplace, the stitches are more apt to pull through the leather from frontto back thereof than they are to pull through the scared and shrunkenedge surface 48. The slight ridges 50 shown in Fig. 6 of the drawingsare the result of the effect of the longitudinal grooves 45 in the tooland may or may not be present, depending on the exact configuration ofthese corrugations 45. The action of the machine on a seam is uniformand there seems to be no tendency to distortion or twisting of the seamas so frequently happens when pressure of a considerable amount isapplied without any such heat treatment as is here utilized.

The application of heat to the searing tool 32 is effected by a flameissuing from the lower end of a nozzle 52 and supplied with anoxyacetylene gas or the like. This enables the temperature of thesearing tool to be raised to a white heat if desired but it has beenfound that a red or cherry heat of a temperature of from 1200 to 1500 F.is suitable.

Having thus described my invention, what I claim as new and desire tosecure by Letters Patent of the United States is:

1. A method of reducing back seams in shoe uppers which consists inapplying to the seam ridge a member heated substantially to red heat toturn part of the ridge to charred fragments and spread the seamlaterally.

2. A method of reducing a seam ridge such as the back seam of a shoewhich consists in apply ing progressively to said ridge heat sufficientto turn part of the ridge to charred fragments and pressure to mold itwhile so heated.

3. A method of reducing seams in articles of leather-like material whichconsists in applying to the edges of the parts at the surface of theseam ridge a destructive heat of approximately 1200 to 1500 F., theapplication of heat being effected progressively along the seam.

4. A method of treating a back seam to reduce it which consists inapplying a destructive heat to the seam ridge along the seams thereby toturn part of the ridge to charred fragments while leaving the seam freeto spread laterally.

5. A method of reducing a back seam which consists in trimming the seamridge by means of from the reduced a tool heated to a temperaturesufiicient to char the material. 6. A method of reducing back seamswhich consists in charring theseam ridge, and removaid o ridge, s me erea 9. In a machine for reducing back seams, a work support, a feedingmember, a searing tool adapted for engagement with the seam ridge, saidtool having a ridge-receiving entrance groove and corrugations beyondsaid groove in the direction of feeding movement, and means for heatingsaid tool.

10. In a, seam-reducing machine, a work-supporting feed r011 adapted forengagement with the display surface of a seamed upper, a grooved 10searing tool adapted for engagement with the seam ridge, means forpressing said tool into firm engagement with the work supported on saidr011, feeding means engageable with the Work adjacent to said tool, andmeans for heating said tool. 15

LIFFQRID K- M Q QNALP:

